In the past we acted in accordance with them without even knowing we were doing this, but now it is different because we know what they are and how they can control us.
In my case, one of my many passions is being judgmental. One day when I was amongst friends I declared to them, probably in an act of being self-righteious, "please show me when I judge people." That very next day my friend said to me, "You know, when you criticize those politicians you heard on the radio or the TV you are being judgmental. We never know if we are being judged in the same way." "Wow", I thought. I didn't even know when I was under the control of this passion and how it impacted others. But, now I knew. It was a key revelation so I could now watch for it and gain control over it, something I still need to watch carefully. This event is one I cannot forget.
We read in Scripture "Be sober, be vigilant" (1Peter 5:8) and "Take head, watch and pray" (Mark 13:33). Saint Theophan helps give meaning to these words.
Watch carefully that some passion does not sneak up, and be careful that it does not deceive you and compel you to do something, whether great or small, to please it.... To watch and be vigilant means not to sleep, not to give yourself over to negligence, but instead to keep your body and soul in a state of alertness. To be sober means not to put your heart into anything else except God... To take head means to watch carefully, so that nothing appears in the heart.In dealing with our passions the first thing is to identify them and learn how they do control us. Then we can control them by being watchful and sober.
Reference: The Spiritual Life, pp 227-230